Pesticides plant-derivates

Folkloric medicine has led many scientists to discover important plant-derived medicines. It has been known for some time that the seeds of several Annonaceous species have an emetic property (Morton, 1987). Eli Lilly, Inc. in 1898 sold a fluid extract made from paw paw seeds A. triloba) for inducing emesis (Anonymous, 1898). Folkloric uses of Annonaceous species also suggest pesticidal properties. The Thai people use extracts of Annona squamosa, A. muricata,A. cherimolia, and A. reticulata for the treatment of head lice (Chumsri, 1995). For this, 10 to 15 fresh leaves of A. squamosa L. are finely crushed and mixed with coconut oil, and the mixture is applied uniformly onto the head and washed off after 30 min. 

Pesticides are chemicals or biological substances used to kill or control pests. They fall into three major classes insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill eelworms, etc.), molluscicides (to kill slugs and snails), and acaricides (to kill mites). These chemicals are typically manmade synthetic organic compounds, but there are exceptions which occur naturally that are plant derivatives or naturally occurring inorganic minerals. 

All manner of pollutants are considered under the discipline of terrestrial ecotoxicology including pesticides, persistent organic pollutants, other organic substances, and metals and metalloids (e.g., selenium and arsenic). Naturally occurring toxins such as those produced by poisonous plants, snakes, or invertebrates generally are not included unless people intentionally apply them for pest control. For example, the pyrethroid pesticides are derived from the naturally occurring pyrethrin toxin that is found in chrysanthemum. 

Biopesticides are substances that are derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. Biopesticides fall into three major classes, including microbial pesticides, plant-incorporated protectants, and biochemical pesticides. Microbial pesticides contain microorganisms, such as bacteria, fungi, and viruses, as their active ingredient. The most widely used microbial pesticides are strains of Bacillus thuringiensis, or Bt. Plant-incorporated protectants are pesticidal substances that plants produce from genetic material that has been added... 

There are hve broad chemical classihcations or categories of pesticides (four for synthetic pesticides and one for natural or plant-derived pesticides). Each of the following hve chemi-cal/biological categories of synthetic and harvested/extracted natural pesticides and growth regulators includes examples of commercial pesticides ... 

Plant derived pesticides Azadirachtin A and B (obtained from Azadirachta indica), Bacillus thuringiensis, Denis (rotenone), Neem oil (obtained from Azadirachta indica), nicotine, pyrethrum, Spinosad (a mixture of spinosyn A and spinosyn D) derived from soil bacterium Saccharopolyspora spinosa. 

Biopesticides include microbial living systems primarily based on bacteria, fungi and viruses. They may also include macro-organisms such as entomopathogenic nematodes, insect predators, and parasites. Biological pesticides may also include plant-derived metabolites as well as insect pheromones and most interestingly... 

Hundreds of applications have been mentioned in the Zweig (1968) review acids, alkaloids, amino acids, antibiotics, antioxidants, food and feed additives, bases and amines, bile acids, carbonyls, dyes, enzymes, lipids, hydrocarbons, hormones, indoles, natural products, peptides, proteins, pesticides, plant growth regulators, pharmaceutical products, phenols, pigments (chlorophylls, xanthophylls, porphyrins, melanin, pterins, pteridines, anthocyanins, ilavonoids, etc.), polymers, purine and pyrimidine derivatives, quinones, RNA, DNA, organic sulfur compounds, steroids, sugars, toxins, vitamins, inorganic ions, and others. 

Among the worldwide total of 30000 known natural products, about 80% stems from plant resources. The number of known chemical structures of plant secondary metabolites is four times the number of known microbial secondary metabolites. Plant secondary metabolites are widely used as valuable medicines (such as paclitaxel, vinblastine, camptothecin, ginsenosides, and artemisinin), food additives, flavors, spices (such as rose oil, vanillin), pigments (such as Sin red and anthocyanins), cosmetics (such as aloe polysaccharides), and bio-pesticides (such as pyrethrins). Currently, a quarter of all prescribed pharmaceuticals compounds in industrialized countries are directly or indirectly derived from plants, or via semi-synthesis. Furthermore, 11% of the 252 drugs considered as basic and essential by the WHO are exclusively derived from plants. According to their biosynthetic pathways, secondary metabolites are usually classified into three large molecule families phenolics, terpenes, and steroids. Some known plant-derived pharmaceuticals are shown in Table 6.1. 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

Pesticides in wastewaters come typically from point sources of contamination such as disposal sites and landfills where industrial or agricultural wastes are buried without any consideration, as well as discharges from industrial effluents from pesticide production plants. Furthermore, nonpoint sources derived from regular agricultural activities, especially in intensive agricultural areas, and accidental spills can also be significant. Urban use of pesticides is also possible in large cities where the use of herbicides and insecticides may result in runoff into the sewers. These sewers in turn may expel pesticides into wastewater treatment plants (WWTPs). 

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